I've said it before and I'll say it again: I think he'll do the series a service. I doubt he'll make the best Halloween movie, but at least he's not a director that's only attached to the product because he knows it will make a buck. The Devil Rejects, while still not a great movie, shows that he knows how to reel things in a bit, and I think he realizes that he has to keep things way reeled in for Halloween, as a showing of reverance for the material.
I can't guarantee he will make a truly good movie - both of his previous movies have high highs and low lows - but at least we have a person with unique vision and a true love of horror flicks is helming it. I'd rather it be Zombie than, say, the people that did the latest two Halloween flicks.
EDIT:
Also, I think McDowell is a good pick for Loomis, btw. In his old age he's managed to become a decent character actor, and I think he'd absolutely nail Loomis's over-the-top rantings about how Michael is PURE EVIL!